Still using the same fuse for the ring magnet after swapping to a 5A SB.
Decided today to go back and try a 4A SB again today Now it can't even do a "grab and drop", will blow that if the ball is coming up the ramp at speed.
Tried a 5A Fast (normal fuse) again and it does "grab and drop" over and over and even could "grab and throw"- but blows while playing a game.
Enjoying the game too much to lose the magnet feature, so put back the original 5A SB which works.
No permanent damage to the game has appeared so far. But I decided to call Stern technical support 1-800-kickers when they open around 9am.
Told Stern the problem with the specified 4A SB fuse rating. That I thought the switches were all good and working in test mode.
To my amazement, Stern said they hadn't heard of this fuse problem. I know my distributor already said he emailed about it. They got me to:
- Start a game, test the magnet with a ball, by holding it just outside the ring on my palm and spinning the spinner with my other hand.
- Banged on the playfield to see if any switches were causing the magnet to fire at the wrong time. That looked OK to me.
- Measure the voltages on a few of the transistor tabs for HV coils which was about 73-74v DC. That's OK (when no load)
- Measure the resistance of the coil at the backboard with my best DMM, I got about 3.3 ohms they said it should read 2.9 but it's near enough.
With the black and read DMM leads touching together, the DMM should say 0 ohms. It showed a few tenths of an ohm, maybe 0.2 ohms.
So I need to test this again after replacing the DMM battery.
After gathering the facts Stern said they would "do some research and get back to me". Had a discussion that you can't use ohms law to calculate the fuse current, as the coil is pulsed by switching the transistor on and off quickly (PCM).
If I had to guess, I'd still say 4A SB is under rated for the application.
